The present invention relates to turbine engines, and more particularly to turbine engines having turbine blades cooled using diverted air.
Turbine engines, such as those used as aircraft turbojets or turbofans typically include from front to rear, in the direction of fluid flow in the engine, fan, compressor, combustion and turbine sections within a housing. These sections include rotating components mounted on one or more coaxial shafts for rotation about a central axis of the engine.
The fan section draws air into the engine. It is compressed in the compressor section, and admixed with fuel in the combustion section where the mixture is ignited. Combustion gases exit the combustion section and drive one or more turbines within the turbine section.
Typically a first stage, high pressure turbine (xe2x80x9cHPTxe2x80x9d) blade is cooled to prevent melting by using uncombusted high pressure air, referred to as xe2x80x9cP3xe2x80x9d air. Specifically, the P3 air is passed through a tangential on-board injector (xe2x80x9cTOBIxe2x80x9d) nozzle. This TOBI nozzle reduces the relative total temperature of the P3 air, typically by approximately 100xc2x0 F. (55xc2x0 C.). The reduced temperature P3 air is passed into a HPT disk/coverplate and through the HPT blade. There, the P3 air cools the HPT blade using, typically using showerhead cooling.
It has however been recognized that the use of high pressure P3 air is thermodynamically inefficient and that a TOBI and ancillary components add weight and complexity to the engine.
As a result, U.S. Pat. No. 6,227,801, the contents of which are hereby incorporated by reference, discloses an improved turbine engine that diverts lower pressure P2x air, at a lower temperature from the compressor section of a turbine engine, upstream of the compressor section""s high pressure (P3) outlet. In order to be effective, however, the P2x air is diverted from a region of the compressor having a pressure higher than the static pressure at the HPT blade. This typically requires that P2x air is diverted after being compressed and heated, as a result of this compression.
Accordingly, an improved method of diverting air for HPT cooling, at reduced temperatures and pressures would be desirable. Moreover, an engine with reduced weight of components associated with HPT cooling is desirable.
It is therefore an object of the present invention to provide an improved turbine engine, in which low temperature air is diverted from a low pressure section of the compressor section of the engine to cool the HPT of the engine. Advantageously, low pressure air is diverted from the compressor section, and its pressure may thereafter be increased. Preferably, the pressure is increased in an intermediate cavity, where rotational energy of the diverted air is converted to static pressure. This may be accomplished by an obstruction within the cavity that converts dynamic head of the air resulting from its tangential velocity in the cavity into static pressure.
In accordance with an aspect of the present invention, a turbine engine includes a compressor section for compressing intake air into high pressure air and intermediate pressure air; a combustion section in flow communication with the cornpressor section, for combusting fuel with compressed air; and a turbine section in flow communication with combustion gases from the combustion section, the turbine section comprising a turbine blade having a tip at lower pressure than the intermediate pressure air. A generally annular cavity upstream of the compressor section includes a bleed in flow communication with the with the intermediate pressure air, and an obstruction within the cavity for converting dynamic head of the intermediate pressure air to increase static pressure of the intermediate pressure air. A conduit having an inlet in flow communication with the cavity and an outlet in flow communication with the turbine blade guides the intermediate pressure air at the increased pressure over the turbine blade.
In accordance with another aspect of the present invention, components within a turbine engine that includes a compressor section, a combustion section, and a turbine section in flow communication are cooled. The method includes (i) diverting intermediate pressure air having a temperature lower than highest pressure air entering the combustion section, from the compressor section; (ii) increasing pressure of the diverted intermediate pressure air to exceed the static pressure of a rotating turbine blade within the turbine section; and (iii) guiding the intermediate pressure air at its increased pressure to the rotating turbine blade to cool the turbine blade.
Other aspects and features of the present invention will become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.